Folding boom rotatable cranes



R. D. S UNDSTROM 3,298,539

FOLDI NG BOOM ROTATABLE CRANES Jan. 17, 1967 Filed Jan. 11, 1965 2 Sheets-Sheet INVEN TOR. F404. 0. 5ulvosneam MA, W 4M 7 ATTORNA'V 9 United States Patent 3,298,539 FOLDING BOQM ROTATABLE CRANES Raul D. Sundstrom, Green Bay, Wis., assignor to Van-L, Ltd., Green Bay, Wis., a corporation of Wisconsin Filed Jan. 11, 1965, Ser. No. 424,764 8 Claims. (Cl. 212-30) This invention relates to improvements in hydraulic circuits for folding boom rotatable cranes.

In another aspect, my invention concerns a hydraulic system for a. boom comprising hingedly related inner and outer boom arms, a hydraulic cylinder connected to one of the arms being placed in series circuit with a hydraulic cylinder for the other arm, effecting great savings in the amount of hydraulic fluid which must be pumped.

In another aspect, my invention concerns a hydraulic system for a boom comprising a pair of hingedly related arms, in which a hydraulic cylinder connected to one of the .arms may be placed in series with a hydraulic cylinder for the other arm, whereby the effective load on the hydraulic cylinder and on the pump is reduced very substantially during horizontal movement of the load.

A further object of the invention is to provide one-way restrictors in the hydraulic lines connecting a boom cylinder to the hydraulic circuit in order to prevent the development of a low pressure area if the load is such that it can drive the hydraulic cylinder fastener than the pump can fill the low pressure side with fluid. The two flow restricters each. permit unrestricted flow in the direction which fills the cylinder from the pump, but restrict the flow to less than the maximum capacity of the pump in the direction of fluid flow away from the hydraulic cylinder.

A further object of the invention is to provide bydraulic cylinders in series circuit for raising and lowering the load on a two-stick boom.

A further object of the invention is to provide a structure in which the effective moment arm of the load on the inner boom cylinder is the length of the inner boom, rather than the length of the entire boom, due to the pivoted center boom link. This link arrangement also maintains the attitude of the outer boom during elevation of the inner boom. Consequently the outer boom does not need to travel as far to place the load on a truck bed after the inner boom has been elevated, since the outer boom never has to be depressed from a raised near-vertical position, but is lowered only from a substantially horizontal position.

A further object of the invention is to provide bydraulic. outrigger cylinders which may be placed in series circuit sothat their fluid volume requirement is only half that of the usual outriggers.

In the drawings:

FIG, 1 is a lateral cross-sectional view of the rear of a vehicle carrying the crane of my invention, the showing of the vehicle being incidental, with a schematic showing of the hydraulic connections in that part of the hydraulic circuit which operates the boom cylinders.

FIG. 2 is a view similar to FIG. 1 showing the boom in a different position.

FIG. 3 is an enlarged top view of the actuating mechanism for rotating the boom.

FIG. 4 is aview similar to FIG. 3 in which the.actuatice ing mechanism is at the other extreme of motion from that portrayed in FIG. 3.

FIG. 5 is a hydraulic circuit diagram. of the circuit, including only those components important to my invention.

As shown in FIGS. 1 and 2, the device of my invention is a crane which may be mounted on a vehicle. It consists generally of an upright shaft carrying an inner boom arm 11 and an outer boom arm 12 at its upper end. Inner boom arm 11 is pivotally related to shaft 10 for movement in a vertical plane and is pivotally related at its other end to outer boom arm 12 for movement in a vertical plane.

An inner link 13, a center link plate 14, and hydraulic cylinders 15 and 16 complete the major structure of the crane itself, which carries a hook. 17 or other apparatus for engaging a load at the outer end of boom section 12.

The entire boom structure is preferably mounted near the front of the bed of a truck. The upright rotatable post, or mast, 10 is supported in bearings mounted on supporting tower 31 secured to a unitary base 32. Secured to each side of tower 31 are pivotal upper horizontal outrigger links 33 and 33 whose outer ends are pivoted at 34 and 34 to vertical outrigger links 35 and 35. Lower horizontal outrigger links 36' and 36' are pivoted to the vertical outrigger links at 37 and 37 and to a fixed portion of the, under side of the truck at 38 and 38, respectively. Outrigger feet 39 and 39' are pivoted at 43 and 43' to the vertical link 35 and 35, respectively. An outrigger cylinder 40 and 40' is pivoted at 34 and 34 to each vertical outrigger link 35 or 35', and the respective piston rods 41, 41' are pivoted to the tower at 42 or 42.

The hydraulic circuit for the Outriggers is shown at FIG. 5. A first pump supplies hydraulic fluid from a reservoir 51 at a pressure controlled by relief'valve 52. One- Way flow is insured by check valve 53. A main fluid duct 54 leads from the pump 50 toward the control valves for the hydraulic cylinders. A branch duct 55 supplies fluid to the outriggers and a branch duct 56 supplies fluid to the boom cylinders.

The control valves and 71 for the outrigger cylinders 40 and 41 are of the type which have a neutral position in which fluid passes through the valve to an exhaust port without going to the hydraulic cylinder, and two actuated positions in which fluid under pressure is furnished to the respective ends of a hydraulic cylinder. These valves are connected in a novel manner. Fluid conduit 55 from pump 50 supplies fluid to inlet port 76 of valve 71. Conduits 74 and 75 connect the valve to respective ends of outrigger cylinder 40.

Valves 70 and 71 are interconnected by fluid passage 72 so that the exhaust port 77 of valve 71 supplies fluid to inlet port 7 6' of valve 70. Exhaust port 77' of valve 70 is connected to sump 51 by conduit 73. Conduit 73 is the return conduit for both valves 70 and 71, and their associated hydraulic cylinders 40 and 40' which operate the Outriggers. This unique way of interconnecting conventional valves 70 and 71 results in a mode of operation in which either valve may be used separately in the normal way, but when both valves are actuated simultaneously, cylinders 40 and 40' are in series circuit. (For purposes of illustration, assume that valves 71 and 70 are each actuated to the left as seen in FIG. 5.) The fluid from the pump 50 and conduit 55 is applied first to one -to maintain, than a simple linkage.

3 end of cylinder 40, Fluidfrom conduit 55 will then be applied to conduit 74 leading to the piston rod end of cylinder 40, retracting the piston rod 41 and raising the right hand outrigger foot 39 from the position shown in FIG. 1 to its retracted position. At the same time, fluid is forced from the end of cylinder 40 nearest to pivot 34, through conduit 75 to the exhaust port 77 of valve 71 through conduit 72 to inlet port 76 of valve 70, then 'through conduit 78 to the end of cylinder 40 nearest piston rod 41, forcing retraction of the left hand outrigger foot 39 from the position-shown in FIG. 1 to the retracted position. Exhaust fluid from the end of the cylinder 40 nearest pivot 34 flows through conduit 79, back to valve 70 and'out exhaust port 77' through conduit 73 to the fluid sump or reservoir 51. If both valves 70 and 71 are actuated to the right, as seen in FIG. 5, the reverse process occurs. Both cylinders 40 and 41 are actuated in a direction to extend them toward the position shown in -FIG. 1 in which the crane is steadied for operation. In that event, the fluid flow is from conduit 55 through inlet port 76 of valve 71 to conduit 75 leading to the end of cylinder 40' nearest pivot 34, urging the right hand outrigger foot 39' to its extended position as shown in FIG. 1. Fluid'exhausted from the end of cylinder 40 through which piston rod 41 extends passes through conduit 74 to valve 71 and out exhaust port 77, conduit 72, inlet port 76 of valve 70, conduit 79 to the end of cylinder 40 nearest pivot 34, and is applied to the piston of cylinder 40 to force the left hand outrigger foot 39 to its extended position as shown in FIG. 1. Exhaust fluid from the end of cylinder 40 through which piston rod 41 extends passes through conduit 7'8 to valve 70 and out exhaust port 77' to conduit 73 to the sump .or reservoir 51. Thus, whenever both valves 70 and 71 are actuated in the same direction, the Outriggers will move simultaneously to the same position. N

All of the valves shown are of the type which are spring-biased to the neutral position. If it is necessary to, adjust one of the Outriggers, for intsance, the left hand outrigger, into contact with the ground after the right hand outrigger has struck the ground, the operator need only release the actuator for valve 71 whereupon it will return to neutral. The hydraulic circuit will then be from conduit 55 through inlet port 76, outlet port 77, conduit 72, inlet port 76' of valve 70, conduit 79 to the pivot 34 and of cylinder 40 to apply pressure to the. piston attached to piston rod 41. Exhaust fluid from the end of cylinder 40 surrounding piston rod 41 will pass through conduit 78, exhaust port 77 and conduit 73 to the reservoir. Thus it will be seen that either cylinder 40 or 40' may be operated independently if needed, but that in normal operation, the operator Will actuate both valves simultaneously in the same direction. In that mode of operation, the two cylinders 40 and 40 will require no more hydraulic fluid than is required to operate either alone. Accordingly, for the same pump capacity, operation will be twice as fast. Pump capacity need never be more than the requirement for one of the cylinders.

Vertical boom shaft 10 is provided with a downward extension to which is secured a radial actuating arm 21 pivoted at 22 to a first curved actuating link 23. Link 23 is in turn pivoted at 25 to a second curved actuating link 24. Link 24 is pivoted at 26 to a fixed anchorpoint.

The second curved actuating link has a pivotal connection 27 with the piston rod 28 of a hydraulic cylinder indicated generally at 29. 1 If piston rod 28 of cylinder 29 were pivoted directly to actuating arm '21, it would not be possible to rotate the boom as much as 180. Other structures may be used to provide the desired freedom of rotation, but they are much more expensive, and difficult The present struct-ure affords approximately 270 of rotation, with a reasonable-piston stroke and no necessity for gearing. The mechanism is not only economical, but is compact.

The boom structure is so arranged that inner boom arm 11, link 13, link plate 14, and vertical mast 11) comprise a form of parallelogram linkage. Thus when inner boom arm 11 is raised by applying pressure to the inner end of cylinder 15, outer boom arm 12 remains generally horizontal, or in whatever attitude it occupied before inner boom arm 11 was raised. This inhibits the high lift capacity of the boom to some extent, but permits a load to be placed on the bed of the truck very rapidly because the outer boom arm 12 does not have to drop from a nearly vertical position through the horizontal position to a depending position. This structure also gives the load an effective moment arm equal to that of the link plate 14, reducing the pressure requirements of the hydraulic cylinders.

A further feature which contributes to rapid operation without excessive use of hydraulic pressure fluid is the hydraulic circuit shown in full, for the purposes of this invention, in FIG. 5, and shown in one of its aspects in FIGS. 1 and 2.

The hydraulic circuit used to operate inner boom cylinder 15 and outer boom cylinder 16 is similar to that used to operate the Outriggers, but in the boom the circuit has still further advantages because of the mechanical construction of the boom and the Way the cylinders are connected to it. Valves and '81 operate cylinders 15 and 16, respectively. The valves are provided with inlet ports 82 and 82' and with'outlet ports 83 and 83. Conduit 84- carries fluid from valve 80 to the end of inner boom cylinder 15 surrounding piston rod 18. Conduit 85 carries fluid between valve 88 and the end of cylinder 15 which is attached to inner boom 11. Conduit 86 carries fluid between valve 81 and the portion of outer boom cylinder 16 surrounding piston rod 19. Conduit 87 carries fluid between valve 81 and the end of cylinder 16 attached to outer boom 12.

In operation, it will be noted that either valve 80 or valve 81 may be actuated separately to position either the inner boom 11 or the outer boom 12, by means of cylinders 15 or 16 respectively. As described above in connection with the Outriggers, the exhaust port 83 of valve 80 is connected through conduit 88 with the intake port 82 of valve 81, and the valves are so arranged that when in their neutral position the intake ports 82, 82 and outlet ports 83, 83' are connected internally of the valve, and the output ports leading to conduits 84, 85, 86, and 87 are sealed.

If a single valve 80 or 81 is actuated, the circuit for the hydraulic cylinder 15 or 16 will be completed through the neutral position of the other valve, since the neutral positions connects ports 82 and 83 for a complete circuit from pump 50 to sump 51. Thus either cylinder 15 or cylinder 16 may be operated independently, despite the interconnection between the valves 80 and 81.

However, when both valves 80 and 81 are actuated, the cylinders are interconnected, as shown in FIGURES 1 and 2.

In the FIGURE 1 position of valves 80 and 81, fluid flows from pump 50 through conduit 56 to port 82, through conduit 84 to the end of cylinder 15 surrounding piston rod 18. As shown in FIG. 1, this is the low volume end of the cylinder. The piston and the piston rod 18 are driven to the right, shortening cylinder 15 and raising inner boom 11. Atthe same time, fluid is driven from the large volume end of cylinder 15, which is nearest boom 11, through conduit 85, flow restrictor and port 83 of valve 80, through conduit 88 to port 82' of valve 81, and through conduit 87 to the low volume end of cylinder 16. As shown in FIG. 1, that is the end nearest outer boom 12. The piston and the piston rod 19 are driven to the left as shown in FIG. 1, lengthening cylinder 16 and permitting outer boom 12 to pivot downwardly under its own weight and the weight of the load on hook 17 (or other material handling means). At the same time, fluid is 'driven from the large volume end of cylinder 16 surrounding piston rod 19 through conduit 86 toport 83' of valve 81 and sent through conduit 100 back to reservoir 51.

In the FIG. 2 position of valves 80 and 81, fluid flows from pump 50 through conduits 54 and 56, through port 82, and through valve 80 to conduit 85 which connects with the end of cylinder 15 which is attached to inner boom arm 11. One-Way flow restrictor 110 does not impede the flow (and in the FIG. 1 position, restrictor 110 does not impede the flow). Return fluid forced out of the piston rod end of cylinder 15 passes through conduit 84 and flow restrictor 110, through valve 80, to exhaust port 83. Conduit 88 carries this fluid to the inlet port 82' of valve 81 and through the valve to conduit 86 which is connected to the piston rod end of cylinder 16. Exhaust fluid from the end of cylinder 16 attached to outer boom arm 12 is forced through conduit 87 and valve 81 to exhaust port 83 and thence through conduit 100 to sump 51.

As shown by FIGS. 1 and 2, the net effect of actuating both valves in the same sense is that inner boom 11 is raised while outer boom 12 is lowered, or vice versa, so that the load is transported laterally, substantially without vertical motion. With a pump having a given output, the transport is twice as fast using this arrangement as it would be with the usual parallel circuit supplying fluid to cylinders 15 and 16. In the alternative, a pump having only half the output volume may be used for the series circuit. The pressure required for an operation of this kind is markedly lower than would be required to raise the inner boom and lower the outer boom in a parallel circuit because of the substantially lateral movement of the load, and because the instant circuit (see FIG. 2) is such as to apply the pressure due to the weight of the load and the boom against the hydraulic fluid in the portion of cylinder 16 surrounding piston rod 19, against the side of cylinder 15 which is bearing the same load. In the FIG. 1 condition of the circuit, low pressure occurs at the end of cylinder 16 attached to outer boom arm 12 due to the weight of the boom and the load. This is balanced by low pressure at the end of cylinder 15 attached to inner boom arm 11, the low pressure areas being connected in the FIG. 1 condition as the high pressure areas are in the FIG. 2 condition. Substantially the only pressure required from the pump in this mode of operation is that required to overcome friction. Substantially no force is required to carry the load. This is in marked contrast to the usual folded boom structure in which there must be pressure in the hydraulic cylinders to support the load at all times. Of course, where the load is raised using a single cylinder, the above condition does not obtain, and sufficient pressure is required to support the load, but in that event only a single hydraulic cylinder is being operated. It is further noted that'the mechanical parallelogram linkage 10, 13, 14, 11, substantially reduces the power requirement of the inner cylinder 15 even in this circumstance. The lever arm of the load is reduced by the parallelogram linkage so that the load in effect is lifted from link plate 14.

The flow restrictors 110 and .110 each act only in one direction, flow toward the cylinder being unrestricted. Flow away from the cylinder is restricted to prevent development of undue low pressure in the side of the hydraulic cylinder being supplied by the pump, when the boom is being moved in a direction in which it is aided by the weight of the boom and the load. Flow under those conditions is restricted just enough so that the pump can keep the cylinder fully supplied with fluid. Thus the restrictor openings 200 are sized according to the maximum load and the pump output. The construction of the restrictors may otherwise be similar to any type of check valve.

A separate pump 57 supplies fluid through a check valve 58 at a pressure determined by a relief valve 59 for the purpose of operating boom rotating cylinder 29. The control valve 60 for the boom rotating cylinder is of the type which has a neutral position shown in FIG. 5 in which fluid is returned to reservoir 51, and both fluid ducts 61 and 62 which supply fluid to hydraulic cylinder 29 are sealed to lock the cylinder 29 in its present position. The valve also possesses two active positions in which the ducts 61 and 62 to cylinder 29 are respectively connected to the pump and the exhaust, or vice versa. Thus the cylinder 29 may be actuated in either direction or locked, in the conventional manner.

I claim:

1. In a boom comprising a first boom arm pivoted to a support, a second boom arm pivoted to said first boom arm, said second boom arm having a free end adapted to engage and lift a load first hydraulic motor means adapted to move said first boom arm vertically about its pivotal connection with said support, sec-0nd hydraulic motor means adapted to move said second boom arm in a vertical plane about its pivotal connection with said first boom arm, and a pump, said motors being divided into first and second fluid containing chambers, said motors being so connected to said boom that the weight of a load tends to reduce the size of said first chambers and increase the size of said second chambers; the improvement comprising hydraulic control means including valves and conduits adapted to interconnect said hydraulic motor means in a series hydraulic circuit with said valves and said pump in at least one control position wherein either said first chambers or said second chambers are placed in communication with each other, whereby the pressures created in one motor by a load are used to balance pressures created in said other motor by a load.

2. The device of claim 1 further comprising one-way flow restrictors in each of the conduits to one said hydraulic motor means to the other elements of said circuit, said restrictors being adapted to permit unrestricted flow toward said motor means and flow away from said motor means restricted slightly less than the total volume of fluid that the pump is adapted to supply to said circuit through said conduits.

3. The device of claim 2 in which the restrictors are in the conduits to said first hydraulic motor means.

4. A load supporting device comprising a pair of relatively movable load supporting members, a pair of fluid actuated devices of equal size respectively connected to said relatively movable load supporting members, and control means for actuating said respective hydraulic fluid devices, said control means being in series with each other and with said devices, each said control means having a normal neutral position in which hydraulic fluid supplied from a pump passes through said control means without actuating said device, and two actuating positions in which hydraulic fluid from said pump is supplied to said hydraulic devices in opposite directions of flow, whereby either device may be actu-' ated separately but when both said load fluid devices are moved simultaneously, they will be in series with each other and require the same amount of hydraulic fluid as one said device.

5. The device of claim 4 in which each said fluid actuated devices comprises a double-acting hydraulic cylinder, said relatively movable load supporting members comprising a pair of pivotally linked boom arms adapted to support a load, each said hydraulic cylinder acting upon a respective boom arm from above, said control means being adapted to series interconnect either the adjacent ends of said cylinders, or the remote ends of said cylinder.

6. The device of claim 5 in which one of said pivotally linked boom arms is provided with a parallel boom arm, a link plate interconnecting adjacent ends of said boom arm and said parallel arm, said hydraulic cylinder connected with the other said boom arm being connected to said link plate as an anchorage.

7. The device of claim 4 further comprising one-way 7 '8 flow restrictors in the conduits to one said hydraulic 2,775,939 7/1950 Rush 21235 motor means, said restrictors being adapted to permit 3,073,456 1/ 1963 Hajek 21266 unrestricted flow toward said motor means and restricted 3,098,395 7/1963 Hagones 21266 X flow away from said motor means. 3,154,199 10/1964 Balogh et a1. 21235 8. The device of claim 7 in which the restrictors are 5 in the conduits to said first hydraulic motor means. FOREIGN PATENTS 1,065,150 9/1959 Germany. References Cited by the Examiner UNITED STATES PATENTS ANDRES H. NIELSEN, Pirzmary Exammer. 2,112,466 3/1938 Maloon 50-52 10 EVON BLUNK Exammer- 2,528,985 11/1950 Wunsch 21266 A.'L. LEVINE, Assistant Examiner. 

1. IN A BOOM COMPRISING A FIRST BOOM ARM PIVOTED TO A SUPPORT, A SECOND BOOM ARM PIVOTED TO SAID FIRST BOOM ARM, SAID SECOND BOOM ARM HAVING A FREE END ADAPTED TO ENGAGE AND LIFT A LOAD FIRST HYDRAULIC MOTOR MEANS ADAPTED TO MOVE SAID FIRST BOOM ARM VERTICALLY ABOUT ITS PIVOTAL CONNECTION WITH SAID SUPPORT, SECOND HYDRAULIC MOTOR MEANS ADAPTED TO MOVE SAID SECOND BOOM ARM IN A VERTICAL PLANE ABOUT ITS PIVOTAL CONNECTION WITH SAID FIRST BOOM ARM, AND A PUMP, SAID MOTORS BEING DIVIDED INTO FIRST AND SECOND FLUID CONTAINING CHAMBERS, SAID MOTORS BEING SO CONNECTED TO SAID BOOM THAT THE WEIGHT OF A LOAD TENDS TO REDUCE THE SIZE OF SAID FIRST CHAMBERS AND INCREASE THE SIZE OF SAID SECOND CHAMBERS; THE IMPROVEMENT COMPRISING HYDRAULIC CONTROL MEANS INCLUDING VALVES AND CONDUITS ADAPTED TO INTERCONNECT SAID HYDRAULIC MOTOR MEANS IN A SERIES HYDRAULIC CIRCUIT WITH SAID VALVES AND SAID PUMP IN AT LEAST ONE CONTROL POSITION WHEREIN EITHER SAID FIRST CHAMBERS OR SAID SECOND CHAMBERS ARE PLACED IN COMMUNICATION WITH EACH OTHER, WHEREBY THE PRESSURES CREATED IN ONE MOTOR BY A LOAD ARE USED TO BALANCE PRESSURES CREATED IN SAID OTHER MOTOR BY A LOAD. 